1. Field of Invention
The invention relates to a universal safety syringe according to the preamble of the main claim.
2. Description of Prior Art
In the case of a number of safety syringes, as are disclosed, for example, in German Patent Specification 43 40 082, the injection cannulas are moved back into the cylinder, after use, in order to remain there permanently and safely, without there being any risk of injury, during further handling of the syringe. However, as in the abovementioned document, a new material is also usually proposed, in this case an elastomeric material for example, or it is no longer possible to use the conventional needles with Luer cone.
In other embodiments, for example the version described in U.S. Pat. No. 5,336,198, even separate means are proposed for the purpose of tilting the cannula laterally in the cylinder in order that it cannot be pushed out again. Unfortunately, all these proposals have in common a not inconsiderable degree of complexity, which makes these safety syringes appear expensive and suitable only for special applications.
Unfortunately, however, there is such a great demand for safety syringes within the medical profession today that safety syringes really have to be in constant use. Up until now, the complex geometries with which the cannulas and/or syringes have been provided has meant that this has not been possible.
In order, however, for it to be possible for safety syringes with a retractable cannula to be established for general usage, a necessary precondition is so-called "downward" compatibility with material which has been used up until now, so that it is also possible to fit the wide variety of cannulas which have been available up until now. Otherwise, it would be necessary for novel cannulas of all sizes to be provided immediately for all conceivable purposes and at all use locations, in order to avoid the two systems coexisting over a transition period--with myriad possibilities of confusion, and problems with storage of double stocks and differing handling methods at the same time.
However, since hitherto known safety syringes require their own cannulas and cannula bases in each case, although it has frequently not been possible to provide or reproach [sic] the desired variety of these, it is essential for it to be possible to continue using the cannulas which have been used up until now.
If, however, use is made of a universal safety syringe with retractable cannula, careless handling of the plunger may cause the latter to be pushed forwards in the cylinder, where it comes into contact with the cannula base before the syringe is actually used. This can take place, for example, as the cannula is pushed on. It goes without saying, however, that it is absolutely essential for this to be avoided because, even during further filling of the syringe, the cannula base is drawn back (too early) into the cylinder - and it is precisely in emergency situations that this may initially go unnoticed.
In the case of hitherto known safety syringes, for example those in DE 38 44 150, this has been avoided by safety elements which were removed prior to injection, in order for it to be possible for the plunger to be pushed right in. For universal usage, however, separate safety elements are highly undesirable since they not only increase the costs of the syringes, but also render handling of the syringes for hitherto conventional usage more complex.